Polyelectrolyte multilayer thin film catalyst and method for producing same

ABSTRACT

Disclosed herein is a catalyst, including, in one example: a carrier, a polymer electrolyte multilayer film formed on the carrier, and metal particles dispersed in the polymer electrolyte multilayer film. The catalyst can be easily prepared, and can be used to produce hydrogen peroxide in high yield in the presence of a reaction solvent including no acid promoter.

RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.13/319,814 filed Nov. 10, 2011, which is a §371 of InternationalApplication No. PCT/KR2010/002137, with an inter-national filing date ofApr. 7, 2010, which claims priority to Korean Patent Application No.10-2009-0041657 filed May 13, 2009, the contents of which areincorporated herein in its entirety.

TECHNICAL FIELD

The present disclosure relates to a catalyst comprising a polymerelectrolyte multilayer film containing metal particles on a carrier, amethod of preparing the catalyst, and a method of directly producinghydrogen peroxide from oxygen and hydrogen using the catalyst.

BACKGROUND

Currently, 95% or more of the total supply of hydrogen peroxide isproduced by an anthraquinone process. However, this anthraquinoneprocess requires a procedure for regenerating an anthraquinone solutionand a procedure for separating hydrogen peroxide from an anthraquinonesolution and refining the separated hydrogen peroxide because manyreaction steps are required to produce hydrogen peroxide and sideproducts are formed in side reactions of the reaction steps [J. M.Campos-Martin, G. Blanco-Brieva, J. L. G. Fierro, Angew. Chem. Int. Ed.,vol. 45, page 6962 (2006)]. Therefore, the production of hydrogenperoxide using an anthraquinone process has high energy consumption andhigh production costs, thus causing the price competitiveness ofhydrogen peroxide to be decreased.

In order to solve the problems of an anthraquinone process, researchinto reactions for directly producing hydrogen peroxide from oxygen andhydrogen that do not produce side products other than water has beenbeing made for a long period of time, but this research is notcommercially available yet due to technical difficulties. This researchis problematic as follows.

First, there is a problem with mixing oxygen and hydrogen. That is, amixture of oxygen and hydrogen can very easily explode because it has alarge explosive range depending on the mixing ratio of oxygen andhydrogen. When the concentration of hydrogen in air at a pressure of 1atm is 4˜75 mol %, the mixture can be exploded by an ignition source.Here, when oxygen is used instead of air, the explodable concentrationof hydrogen is enlarged to 4˜94 mol %. This explodable concentration ofhydrogen is enlarged depending on the increase of pressure, thusincreasing the explodability of the mixture [C. Samanta, V. R.Choudhary, Catal. Commun., vol. 8, page 73 (2007)]. Therefore, in theprocess of directly producing hydrogen peroxide using hydrogen andoxygen as reactants, the mixing ratio of hydrogen and oxygen iscontrolled within a safe range, and the concentration of hydrogen andoxygen is diluted with an inert gas such as nitrogen or carbon dioxide.

In addition to the above safety problem, there is another problem, whichis that hydrogen peroxide, although produced, easily decomposes intowater and oxygen because it is a very unstable compound, and it is noteasy to acquire high hydrogen peroxide selectivity because a catalystused to produce hydrogen peroxide is used to synthesize water.Therefore, in conducting research into reactions for directly producinghydrogen peroxide from oxygen and hydrogen, strong acids and halideadditives together with high-activity catalysts have been researched inorder to solve the above problems.

Reactions for directly producing hydrogen peroxide have been conductedusing precious metal catalysts, such as gold, platinum, palladium andthe like [P. Landon, P. J. Collier, A. J. Papworth, C. J. Kiely, G. J.Hutchings, Chem. Commun., page 2058 (2002); G. Li, J. Edwards, A. F.Carley, G. J. Hutchings, Catal. Commun., vol. 8, page 247 (2007); D. P.Dissanayake, J. H. Lunsford, J. Catal., vol. 206, page 173 (2002); D. P.Dissanayake, J. H. Lunsford, J. Catal., vol. 214, page 113 (2003); P.Landon, P. J. Collier, A. F. Carley, D. Chadwick, A. J. Papworth, A.Burrows, C. J. Kiely, G. J. Hutchings, Phys. Chem. Chem. Phys., vol. 5,page 1917 (2003); J. K. Edwards, B. E. Solsona, P. Landon, A. F. Carley,A. Herzing, C. J. Kiely, G. J. Hutchings, J. Catal., vol. 236, page 69(2005); J. K. Edwards, A. Thomas, B. E. Solsona, P. Landon, A. F.Carley, G. J. Hutchings, Catal. Today, vol. 122, page 397 (2007); Q.Liu, J. C. Bauer, R. E. Schaak, J. H. Lunsford, Appl. Catal. A, vol.339, page 130 (2008)]. Among the precious metal catalysts, the palladiumcatalyst is reported to exhibit relatively excellent activity, and thispalladium catalyst is generally used in a state in which it is supportedon a carrier, such as alumina, silica, carbon or the like.

Further, in order to improve the selectivity of hydrogen peroxide, acidis added to a solvent to prevent hydrogen peroxide from decomposing intowater and oxygen, and halogen ions are added to a solvent or a catalystto prevent oxygen and hydrogen from forming water [Y.-F. Han, J. H.Lunsford, Catal. Lett., vol. 99, page 13 (2005); Y.-F. Han, J. H.Lunsford, J. Catal., vol. 230, page 313 (2005); V. R. Choudhary, C.Samanta, J. Catal., vol. 238, page 28 (2006); V. R. Choudhary, P. Jana,J. Catal., vol. 246, page 434 (2007); C. Samanta, V. R. Choudhary,Catal. Commun., vol. 8, page 73 (2007); C. Samanta, V. R. Choudhary,Appl. Catal. A, vol. 326, page 28 (2007); V. R. Choudhary, C. Samanta,T. V. Choudhary, Catal. Commun., vol. 8, page 1310 (2007)]. Suchadditives, such as acid and halogen ions, serve to improve theselectivity of hydrogen peroxide, but cause the problems of corrosion,of elution of a metal, such as palladium or the like, supported on acarrier, thus decreasing catalytic activity; and, of requiring thathydrogen peroxide be separated and refined even after it is produced.Meanwhile, P. F. Escrig et al. reported that, when a palladium catalystcontaining an ion exchange resin having a sulfonic acid group and acomplex is used, high catalytic activity is exhibited even when only avery small amount of halogen ions is added without the addition of acid(U.S. Pat. Nos. 6,822,103 and 7,179,440).

Recently, various methods using nanotechnologies have been attempted inorder to develop a high-activity catalyst which can be efficiently usedto directly produce hydrogen peroxide from oxygen and hydrogen. Forexample, Q. Liu et al. developed a catalyst in which palladiumnanoparticles are supported on active carbon (Q. Liu, J. C. Bauer, R. E.Schaak, J. H. Lunsford, Angew. Chem. Int. Ed., vol. 47, page 6221(2008)), B. Zhou et al. insisted that nanoparticles phase-controlled by110 plane exhibit excellent activity (U.S. Pat. Nos. 6,168,775 and6,746,597), and J. Edwards reported that a catalyst in which apalladium-gold binary metal is supported on active carbon treated withnitric acid exhibits excellent hydrogen selectivity (J. K. Edwards, B.Solsona, D. Ntainjua, A. F. Carley, A. A. Herzing, C. J. Kiely, G. J.Hutchings, Science, vol. 323, page 1037 (2009)). However, in order touse the highly-dispersed nanoparticles as a catalyst, many technicaldifficulties, such as mass production, the prevention of metal elution,the prevention of sintering phenomenon in reaction, and the change incatalytic activity according to the phase transition of metal catalystparticles, must be overcome.

As described above, the method of directly producing hydrogen peroxidefrom oxygen and hydrogen has been researched for a long period of timedue to its technical importance, but is still being researchedacademically and is limited to research into small-scale catalystproduction and catalytic reaction. Therefore, in order to commercializethis method, it is keenly required to develop a catalyst which can beeasily produced and which can exhibit remarkably excellent performanceeven under the reaction condition that additives, such as acids, halogenions and the like, are used at a minimum.

SUMMARY

Hereupon, the present inventors have made efforts to develop a catalystwhich can be produced and which can exhibit high activity in theproduction of hydrogen peroxide. As a result, they found that a catalystin which a polymer electrolyte multilayer film containing metalparticles is formed on a carrier can be used to obtain a high yield ofhydrogen peroxide compared to conventional catalysts and that thiscatalyst exhibits high activity even under the condition that only avery small amount of halogen ions is added without the addition ofacids. Based on the findings, the present disclosure was completed.

Accordingly, the present disclosure provides a catalyst which canexhibit high activity in various reactions.

Further, the present disclosure provides a method of forming a polymerelectrolyte multilayer film containing metal particles on a carrier.

Furthermore, the present disclosure provides a method of directlyproducing hydrogen peroxide from oxygen and hydrogen using the catalyst.

An aspect of the present disclosure provides a catalyst, including: acarrier, a polymer electrolyte multilayer film formed on the carrier;and metal particles dispersed in the polymer electrolyte multilayerfilm.

Another aspect of the present disclosure provides a method of preparinga catalyst, including: forming a polymer electrolyte multilayer film ona carrier; dispersing metal precursors in the polymer electrolytemultilayer film; and reducing the metal precursors to metals using areducing agent.

Still another aspect of the present disclosure provides a method ofpreparing a catalyst, including: forming a polymer electrolytemultilayer film complexed with metal precursors on a carrier; andreducing the metal precursors to metal particles using a reducing agent.

Still another aspect of the present disclosure provides a method ofproducing hydrogen peroxide from hydrogen and oxygen using the catalyst.

As described above, the catalyst according to the present disclosurediscloses that metal particles are strongly bonded between the layers ofa polymer electrolyte multilayer film, so that the elution of metal doesnot occur during a reaction., with the result that the activity of thecatalyst does not deteriorate. Further, the catalyst according to thepresent disclosure discloses that the kind and pH of polymerelectrolytes and the layer number of the polymer electrolyte multilayerfilm are adjusted, thus adjusting the concentration and particle size ofthe metal dispersed in the polymer electrolyte multilayer film.Furthermore, the catalyst according to the present disclosure disclosesthat it can be easily prepared, and in that it can be used to increaseactivity in various reactions using metal particles as a catalyst aswell as to produce hydrogen peroxide.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view showing a method of preparing a catalyst bysequentially and alternately stacking cationic polymer electrolytes andanionic polymer electrolytes on an anionic carrier to form a polymerelectrolyte multilayer film, mixing the polymer electrolyte multilayerfilm with a metal precursor solution to form metal ions and thenreducing the metal ions to metals;

FIG. 2 is a schematic view showing a method of preparing a catalyst bysequentially and alternately stacking cationic polymer electrolytes andanionic polymer electrolytes complexed with metal precursors on ananionic carrier to form a polymer electrolyte multilayer film and thenreducing metal ions to metals;

FIG. 3 is a schematic view showing a method of preparing a catalyst bysequentially and alternately stacking cationic polymer electrolytes andanionic polymer electrolytes on a cationic carrier to form a polymerelectrolyte multilayer film, mixing the polymer electrolyte multilayerfilm with a metal precursor solution to form metal ions and thenreducing the metal ions to metals; and

FIG. 4 is a schematic view showing a method of preparing a catalyst bysequentially and alternately stacking anionic polymer electrolytes andcationic polymer electrolytes complexed with metal precursors on acationic carrier to form a polymer electrolyte multilayer film and thenreducing metal ions to metals.

DETAILED DESCRIPTION

Hereinafter, exemplary embodiments of the present disclosure will bedescribed in detail with reference to the attached drawings.

An embodiment of the present disclosure provides a catalyst, including:a carrier; a polymer electrolyte multilayer film formed on the carrier;and metal particles dispersed in the polymer electrolyte multilayerfilm.

The carrier may be electrically charged such that cationic or anionicpolymer electrolytes are easily anchored thereon. Therefore, the carriermay be a cationic resin or an anionic resin.

As the cationic resin used as the carrier, a polymer resin having acationic functional group selected from the group consisting of asulfonic acid group, a carboxylic acid group, a phosphoric acid groupand a phosphonic acid group may be used. The polymer resin having thecationic functional group may include one or more selected from amongpolybenzimidazole, polyimide, polyetherimide, polyphenylene sulfide,polysulfone, polyether sulfone, polyether ketones, polyether-etherketones, polyphenyl quinoxaline and fluorine polymer, and, preferably,may include one or more selected from among poly(perfluorosulfonic acid)(commercially supplied as “Nafion”), poly(perfluorocarboxylic acid), asulfonic acid group-containing copolymer of tetrafluoroethylene andfluorovinylether, defluorinated polyetherketone sulfide, aryl ketones,poly[2,2′-(m-phenylene)-5,5′-bibenzimidazole], andpoly(2,5-benzimidazole).

The anionic resin used as the carrier may be selected from among halogencompound resins, bicarbonate resins, carbonate resins, hydroxide resin,and mixtures thereof. Examples of the halogen compound resins aredescribed in JP-A-57-139026 (cited as a reference). Examples of thebicarbonate resins are described in WO 95-20559, WO 97-33850, RU Pat.Nos. 2002726 and 2001901 (cited as references). Examples ofcommercially-available anionic resins may include Amberlite™ IRA 400 and900 (polystyrene resin crosslinked with divinyl benzene, manufactured byRohm and Haas), Lewatit™ M 500 WS (manufactured by Bayer), Duolite™ A368, A-101D, ES-131 and A-161 (manufactured by Rohm and Haas), andDOWEX™ MSA-1, MARATHON A and MARATHON MSA (manufactured by Dow Chemicalcompany), and the like.

In the present disclosure, a nonionic carrier may be used in addition tothe ionic carrier. The kind of the nonionic carrier is not limited aslong as electrically-charged polymer electrolytes can be formed thereon.Examples of the nonionic carrier may include active carbon, silica,alumina, silica-alumina, zeolite and other materials well known in therelated field, preferably, alumina. This nonionic carrier is generallyused in the art because it is cheaper than the ionic carrier. Therefore,in the present disclosure, the nonionic carrier, such as alumina, may beused for purposes of cost reduction although its efficiency is equal toor lower than that of the ionic carrier.

The polymer electrolyte anchored on the carrier includes a cationicpolymer electrolyte and an anionic polymer electrolyte. The cationicelectrolyte may be at least one selected from the group consisting ofpoly(allylamine), polydiallyldimethylanunonium, poly(ethylenediamine)and poly(acrylamide-co-diallyldimethylammonium), but is not limitedthereto. Further, the anionic electrolyte may be at least one selectedfrom the group consisting of poly(4-styrenesulfonate), poly(acrylicacid), poly(acrylamide), poly(vinylphosphonic acid),poly(2-acrylamido-2-methyl-1′-propanesulfonic acid), poly(anetholesulfonic acid) and poly(vinylsulfonate), but is not limited thereto. Avariety of polymer electrolytes, such as the cationic polymerelectrolytes and the anionic polymer electrolytes, are used, so that theion bonding strength of the polymer electrolyte can be adjusted, withthe result that metal particle size can be adjusted when metalprecursors are reduced using a reducing agent.

In the present disclosure, when a polymer electrolyte multilayer film isformed using a polymer electrolyte, the thickness of the polymerelectrolyte multilayer film is controlled by adjusting the molecularweight of the polymer electrolyte, thus controlling the concentrationand particle size of the metal dispersed in the polymer electrolytemultilayer film. In this case, the polymer electrolyte may have amolecular weight of 1,000˜1,000,000, preferably, 2,000˜500,000. Forexample, PAH (poly(allylamine)hydrochloride) may have a molecular weightof 3,000˜20,000, preferably, 4,000˜12,000.

The polymer electrolyte multilayer film of the present disclosure has alayer number of 2˜30, preferably, 2˜15. The catalyst of the presentdisclosure is characterized by the fact that metal particles are notdisposed on the surface of a carrier but between polymer electrolytes.For this reason, the catalyst including the polymer electrolytemultilayer film has more excellent activity than a catalyst including apolymer electrolyte monolayer film. Therefore, when the layer number ofa polymer electrolyte multilayer film is less than 2, the polymerelectrolyte multilayer film of the present disclosure cannot be formed.Further, when the layer number thereof is more than 30, the activity ofthe catalyst is not greatly changed, and thus it is unnecessary to forma polymer electrolyte multilayer having a layer number of greater than30.

The metal particles dispersed in the polymer electrolyte multilayer filmare selected from among palladium (Pd), platinum (Pt), ruthenium (Ru),rhodium (Rh), iridium (Ir), silver (Ag), osmium (Os), nickel (Ni),copper (Cu), cobalt (Co), titanium (Ti) and mixtures thereof,preferably, palladium (Pd), platinum (Pt) and a mixture thereof. Thesemetal particles are formed by dispersing metal precursors in polymerelectrolytes and then reducing the dispersed metal precursors using areducing agent. Examples of the palladium-containing metal precursorsused in the present disclosure containing palladium (Pd) include, butare not limited to, tetrachloroplatinic acid(II) (H₂PtCl₄),hexachloroplatinic acid(IV) (H₂PtCl₆), potassiumtetrachloroplatinate(II) (K₂PtCl₄), potassium hexachloroplatinate(IV)(H₂PtCl₆), and mixtures thereof.

Further, the metal particles of the present disclosure, which can bevariously adjusted according to the purpose of use, may have an averageparticle size of 1˜1,000 nm, preferably 1˜500 nm, and more preferably1˜100 nm.

Another embodiment of the present disclosure provides a method ofpreparing a catalyst, including the steps of: (a) alternately applying afirst polymer electrolyte solution and a second polymer electrolytesolution to a carrier to form a polymer electrolyte multilayer film onthe carrier, wherein the first polymer electrolyte solution and thesecond polymer electrolyte solution are different from each other, andare cationic or anionic electrolyte solutions, respectively; (b)applying a metal precursor solution to the carrier including the polymerelectrolyte multilayer film formed thereon to disperse metal precursorsin the polymer electrolyte multilayer film; and (c) reducing the metalprecursors dispersed in the polymer electrolyte multilayer film tometals using a reducing agent.

This method of preparing a catalyst can be performed in various mannersaccording to the kind of the electric charge of the carrier and theorder of the polymer electrolyte solutions. Examples of the variousmanners are as follows.

In the first manner, the catalyst is prepared by a process of forming apolymer electrolyte multilayer film containing metal particles on acarrier, including the steps of: (a) applying a cationic polymerelectrolyte on an anionic resin having a sulfonic acid group (SO₃ ⁻)using distilled water as a solvent to form a cationic polymerelectrolyte layer; (b) applying an anionic polymer electrolyte on thecationic polymer electrolyte layer to form an anionic polymerelectrolyte layer; (c) repeatedly laminating the cationic polymerelectrolyte layer and the anionic polymer electrolyte layer to form apolymer electrolyte multilayer film; (d) immersing the polymerelectrolyte multilayer film into a metal precursor solution to dispersemetal ions in the polymer electrolyte multilayer film; and (e) reducingthe metal ions dispersed in the polymer electrolyte multilayer film tometals using a reducing agent.

In the second manner, the catalyst is prepared by a process of forming apolymer electrolyte multilayer film containing metal particles on acarrier, including the steps of: (a) applying an anionic polymerelectrolyte on a halogen-containing cationic resin (NR₃ ⁺Cl⁻) usingdistilled water as a solvent to form an anionic polymer electrolytelayer; (b) applying a cationic polymer electrolyte on the anionicpolymer electrolyte layer to form a cationic polymer electrolyte layer;(c) repeatedly laminating the anionic polymer electrolyte layer and thecationic polymer electrolyte layer to form a polymer electrolytemultilayer film; (d) immersing the polymer electrolyte multilayer filminto a metal precursor solution to disperse metal ions in the polymerelectrolyte multilayer film; and (e) reducing the metal ions dispersedin the polymer electrolyte multilayer film to metals using a reducingagent.

In the method of preparing a catalyst according to the presentdisclosure, examples of the solvent for dissolving the polymerelectrolyte may include water, n-hexane, ethanol, triethylamine,tetrahydrofuran (THF), dimethyl sulfoxide (DMSO), ethyl acetate,isopropyl alcohol, acetone, acetonitrile, benzene, butyl alcohol,chloroform, diethyl ether, and mixtures thereof.

Further, in the method of preparing a catalyst according to the presentdisclosure, the cationic or anionic polymer electrolyte solution mayhave a pH of 8˜11, preferably 8˜10, and the metal precursor solution mayhave a pH of 2˜6, preferably 4˜6, more preferably 2˜4. When the pH ofthe cationic polymer electrolyte solution or the anionic polymerelectrolyte solution is adjusted, the thickness of the polymerelectrolyte multilayer film can be adjusted, thereby adjusting theconcentration and particle size of the metals dispersed in the polymerelectrolyte multilayer film.

Further, in the method of preparing a catalyst according to the presentdisclosure, in addition to a metal precursor dissolved in a generalsolvent such as distilled water or the like, a metal precursor dissolvedin a solution whose pH is adjusted by the addition of acid or base maybe used as the metal precursor used in this method. The two metalprecursors may be used at the same time.

Further, in the method of preparing a catalyst according to the presentdisclosure, examples of the reducing agent used to reduce the metalprecursors include, but are not limited to, chemical reducing agents andhydrogen. The reducing agent may be one or more selected from amongsodium borohydride (NaBH₄), hydrazine (N₂H₄), sodium formate (HCOONa),ammonium hydrogen carbonate (NH₄HCO₃), and hydrogen (H₂), and,preferably, may be sodium borohydride (NaBH₄) or hydrogen (H₂).

In the present disclosure, in order to form a polymer electrolytemultilayer film containing metal particles on a carrier, another methodmay be used in addition to the above method. Therefore, still anotheraspect of the present disclosure provides a method of preparing acatalyst, including the steps of: (a) alternately applying a firstpolymer electrolyte solution and a second polymer electrolyte solutionto a carrier to form a polymer electrolyte multilayer film on thecarrier, wherein the first polymer electrolyte solution and the secondpolymer electrolyte solution are cationic or anionic electrolytesolutions different from each other, and at least one of the firstpolymer electrolyte solution and the second polymer electrolyte solutionincludes metal precursors complexed therewith; and (b) reducing themetal precursors dispersed in the polymer electrolyte multilayer film tometals using a reducing agent.

This method of preparing a catalyst can be performed in various mannersaccording to the kind of electric charge of the carrier and the kind andorder of the polymer electrolyte solutions or the polymer electrolytesolutions complexed with metal precursors. Examples of the variousmanners are as follows.

In the first manner, the catalyst is prepared by a process of forming apolymer electrolyte multilayer film containing metal particles on acarrier, including the steps of: (a) applying a cationic polymerelectrolyte on an anionic resin having a sulfonic acid group (SO₃ ⁻)using distilled water as a solvent to form a cationic polymerelectrolyte layer; (b) applying an anionic polymer electrolyte complexedwith metal ions on the cationic polymer electrolyte layer to form ananionic polymer electrolyte layer; (c) repeatedly laminating thecationic polymer electrolyte layer and the anionic polymer electrolytelayer to form a polymer electrolyte multilayer film; (d) immersing thepolymer electrolyte multilayer film into a metal precursor solution todisperse metal ions in the polymer electrolyte multilayer film; and (e)reducing the metal ions dispersed in the polymer electrolyte multilayerfilm to metals using a reducing agent.

In the second manner, the catalyst is prepared by a process of forming apolymer electrolyte multilayer film containing metal particles on acarrier, including the steps of: (a) applying an anionic polymerelectrolyte on a halogen-containing cationic resin (NR₃ ⁺Cl⁻) usingdistilled water as a solvent to form an anionic polymer electrolytelayer; (b) applying a cationic polymer electrolyte complexed with metalions on the anionic polymer electrolyte layer to form a cationic polymerelectrolyte layer; (c) repeatedly laminating the anionic polymerelectrolyte layer and the cationic polymer electrolyte layer to form apolymer electrolyte multilayer film; (d) immersing the polymerelectrolyte multilayer film into a metal precursor solution to dispersemetal ions in the polymer electrolyte multilayer film; and (e) reducingthe metal ions dispersed in the polymer electrolyte multilayer film tometals using a reducing agent.

The polymer electrolyte multilayer film formed by the method of thepresent disclosure is very physically and chemically stable because itsrespective layers are interconnected by electrostatic interaction,hydrogen bonding, van der Waals interaction or covalent bonding. Themetals dispersed in the polymer electrolyte multilayer film are disposedin the form of encapsulation or embedment. Further, these metals arestrongly connected with the polymer electrolyte multilayer film byelectrostatic interaction, hydrogen bonding, van der Waals interactionor covalent bonding. Therefore, one of the problems of conventionalcatalysts supported with metal, that is, the problem that catalyticactivity is deteriorated by the elution occurring during reactions, canbe basically solved by the method of preparing a catalyst by dispersingmetal particles in the polymer electrolyte polymer according to thepresent disclosure.

Further, still another aspect of the present disclosure provides amethod of preparing hydrogen peroxide from hydrogen and oxygen using thecatalyst under the condition that a reaction solvent does not include anacid promoter.

The production of hydrogen peroxide may be performed by a liquid phasereaction using methanol, ethanol or water as a solvent (reactionmedium). Oxygen and hydrogen, serving as reactants, may be used in theform of a gas mixture diluted with nitrogen in order to prevent thedanger of explosion. In this case, the reaction of oxygen and hydrogento form hydrogen peroxide may be conducted using a tubular reactorprovided with a cooling water jacket at a reaction pressure of 30˜60bar, preferably, 45˜55 bar and a reaction temperature of 20˜40° C.,preferably, 20˜30° C. while maintaining the volume ratio ofhydrogen:oxygen:nitrogen at 3:40:57 and maintaining the supply ratio ofthe total amount of gas to the amount of solvent at about 3200.

In the reaction of producing hydrogen peroxide by the reaction of oxygenand hydrogen, only a very small amount of a halogen additive may beadded without the addition of strong acid in order to prevent a reactorfrom being corroded. As the halogen additive, hydrobromic acid, sodiumbromide (NaBr), potassium bromide (KBr) or the like may be used. Theconcentration of the halogen additive may be 1˜100 ppm, preferably 5˜50ppm, more preferably 10˜20 ppm, based on the amount of methanol used asa solvent.

Hereinafter, the present disclosure will be described in more detailwith reference to the following Examples. Here, these examples are setforth to illustrate the present disclosure, but are not to be construedas the limit of the present disclosure.

In the following Examples, in order to compare the activity of catalystsused in the reaction of directly preparing hydrogen peroxide from oxygenand hydrogen, reaction times were set at 150 hours if not otherwisementioned.

Example 1 Forming a Polymer Electrolyte Multilayer Film on an AnionicCarrier

A method of forming a polymer electrolyte multilayer film containingmetal particles on an anionic resin having a sulfonic acid group (SO₃)was conducted as follows. All processes of the method were conducted atroom temperature.

First, a 10 mM PAH (Poly(allyamine)hydrochloride, molecular weight56,000) aqueous solution and a 10 mM PSS (Poly(4-styrenesulfonate),molecular weight 70,000) aqueous solution were prepared, and then the pHof each of the aqueous solutions was adjusted to 9 using hydrochloricacid and sodium hydroxide. K₂PdCl₄, serving a palladium precursor, wasdissolved in distilled water to form a K₂PdCl₄ aqueous solution having apH of 3.

10 g of an anionic resin having a sulfonic acid group (SO₃) was washedwith 300 mL of distilled water for 10 minutes three times. The distilledwater was removed, and then 300 mL of the 10 mM PAH aqueous solution wasput into a beaker filled with the anionic resin having a sulfonic acidgroup (SO₃ ⁻) and then stirred for 20 minutes. The solution remaining inthe beaker was removed, and then the resulting product was furtherwashed with 300 mL of distilled water for 5 minutes three times to forma PAH layer on the anionic resin.

The anionic resin including the PAH layer formed thereon was put into abeaker filled with 300 mL of the 10 mM PSS aqueous solution and thenstirred for 20 minutes. The solution remaining in the beaker wasremoved, and then the resulting product was further washed with 300 mLof distilled water for 5 minutes three times. Thereafter, theseprocesses were repeatedly performed to form a polymer electrolytemultilayer film having a layer number of 7.

The anionic resin including the polymer electrolyte multilayer filmformed thereon was put into a beaker filled with 250 mL of the 1 mMK₂PdCl₄ aqueous solution and then stirred for 30 minutes. The solutionremaining in the beaker was removed, and then the resulting product wasfurther washed with 300 mL of distilled water for 5 minutes three timesto disperse metal ions in the polymer electrolyte multilayer film formedon the anionic resin.

The anionic resin including the polymer electrolyte multilayer filmdispersed with the metal ions was put into a beaker filled with 300 mLof distilled water and then stirred, and simultaneously 20 mL of a 50 mMNaBH₄ aqueous solution was dripped thereto to reduce the metal ionsdispersed in the polymer electrolyte multilayer film. After the stirringwas further performed for 30 minutes, the solution remaining in thebeaker was removed, and then the resulting product was further washedwith 300 mL of distilled water for 5 minutes three times, therebypreparing a catalyst. A method of producing hydrogen peroxide by thereaction of oxygen and hydrogen using the catalyst prepared through theabove processes is conducted as follows.

10 cc of the catalyst was charged in a tubular reactor provided with acooling water jacket, and was then washed with methanol for 3 hours at areaction pressure of 1 bar and a reaction temperature of 25° C.Subsequently, methanol containing 15 ppm of HBr was used as a solventinstead of the methanol and the reaction temperature was increased to 50bars, and then the reaction of producing hydrogen peroxide was conductedin a state in which the volume ratio of hydrogen:oxygen:nitrogen wasmaintained at 3:40:57 and the supply ratio of the total amount of gas tothe amount of solvent was maintained at about 3200. After the reaction,the yield of hydrogen peroxide was calculated by titration, and theselectivity of hydrogen was analyzed by gas chromatography. The resultsthereof are given in Table 1.

Examples 2 to 9 Forming Polymer Electrolyte Multilayer Films on AnionicCarriers

Polymer electrolyte multilayer films were formed in the same manner asExample 1 while changing the kinds of cationic/anionic polymerelectrolytes, the pH of aqueous polymer electrolyte solutions and thelayer number of the polymer electrolyte multilayer films. Further,methods of evaluating the activity of catalysts were conducted in thesame manner as Example 1.

In these Examples, PAH (Poly(allyamine)hydrochloride, molecular weight56,000), PDDA (Polydiallyldimethylammonium, molecular weight 100,000)and PEI (Poly(ethyleneimine), molecular weight 25,000) were used as thecationic polymer electrolytes, and PSS (Poly(4-styrenesulfonate),molecular weight 70,000) and PAA (Poly(acrylic)acid) were used as theanionic polymer electrolytes.

The preparation conditions and activity evaluation results of thecatalysts are given in Table 1.

TABLE 1 Layer Cationic polymer Anionic polymer number of Pd H₂O₂ H₂electrolyte electrolyte multilayer content yield selectivity Ex. kindconc. pH kind conc. pH film (wt %) (wt %) (%) 1 PAH 10 mM  9 PSS 10 mM9   7 0.29 8.0 71 2 PAH 10 mM  9 PSS 10 mM 9   5 0.21 6.8 70 3 PAH 10 mM 9 PSS 10 mM 9   9 0.35 8.5 68 4 PDDA 10 mM  9 PSS 10 mM 9   7 0.25 7.270 5 PEI 1 g/L  5 PSS 10 mM 9   7 0.30 5.8 63 6 PEI 1 g/L 10 PSS 10 mM9   7 0.33 5.2 65 7 PAH 10 mM  9 PAA 10 mM 3.5 7 0.27 6.2 68 8 PDDA 10mM  9 PAA 10 mM 3.5 7 0.10 2.8 68 9 PEI 1 g/L  5 PAA 10 mM 3.5 7 0.081.9 60

Example 10 Forming a Polymer Electrolyte Multilayer Film on a Cationic(Strongly Basic) Carrier

A method of forming a polymer electrolyte multilayer film containingmetal particles on a halogen-containing strongly basic cationic (NR₃⁺Cl⁻) resin was conducted as follows. All processes of the method wereconducted at room temperature.

10 g of a halogen-containing strongly basic cationic (NR₃ ⁺Cl⁻) resinwas washed with 300 mL of distilled water for 10 minutes three times.The distilled water was removed, and then 300 mL of a 10 mM PSS aqueoussolution was put into a beaker filled with the halogen-containingstrongly basic cationic (NR₃ ⁺Cl⁻) resin and then stirred for 20minutes. The solution remaining in the beaker was removed, and then theresulting product was further washed with 300 mL of distilled water for5 minutes three times to form a PSS layer on the cationic resin.

The cationic resin including the PSS layer formed thereon was put into abeaker filled with 300 mL of a 10 mM PAH aqueous solution and thenstirred for 20 minutes. The solution remaining in the beaker wasremoved, and then the resulting product was further washed with 300 mLof distilled water for 5 minutes three times. These processes wererepeatedly performed to form a polymer electrolyte multilayer filmhaving a layer number of 6.

Thereafter, a polymer electrolyte multilayer film dispersed with metalions was formed on the halogen-containing strongly basic cationic (NR₃⁺Cl⁻) resin in the same manner as Example 1, thereby preparing acatalyst.

Hydrogen peroxide was produced by the reaction of oxygen and hydrogenusing the catalyst in the same manner as Example 1.

Examples 11 to 15 Forming Polymer Electrolyte Multilayer Films onCationic (Strongly Basic) Carriers

Polymer Electrolyte Multilayer Films were Formed in the Same Manner asExample 10 while changing the kinds of cationic/anionic polymerelectrolytes, the pH of aqueous polymer electrolyte solutions and thelayer number of the polymer electrolyte multilayer films. Further,methods of evaluating the activity of catalysts were conducted in thesame manner as Example 1.

The preparation conditions and activity evaluation results of thecatalysts are given in Table 2.

TABLE 2 Layer Cationic polymer Anionic polymer number of Pd H₂O₂ H₂electrolyte electrolyte multilayer content yield selectivity Ex. kindconc. pH kind conc. pH film (wt %) (wt %) (%) 10 PSS 10 mM 9 PAH 10 mM 96 0.17 5.3 70 11 PSS 10 mM 9 PDDA 10 mM 9 6 0.21 5.5 69 12 PSS 10 mM 9PEI 1 g/L 5 6 0.25 3.5 64 13 PAA 10 mM 9 PAH 10 mM 9 6 0.22 4.2 67 14PAA 10 mM 9 PDDA 10 mM 9 6 0.10 2.0 67 15 PAA 10 mM 9 PEI 1 g/L 5 6 0.111.7 62

Example 16 Forming a Polymer Electrolyte Multilayer Film on a Cationic(Weakly Basic) Carrier

A polymer electrolyte multilayer film was formed in the same manner asExample 10, except that an ammonia-containing weakly basic cationicresin was used as a carrier. Further, the evaluation of the activity ofa catalyst was conducted in the same manner as Example 10. As a result,the prepared catalyst includes 0.2% of palladium, and, as the result ofevaluating the activity of the catalyst, the yield of hydrogen peroxideis 5.4 wt %, and the selectivity of hydrogen is 68%.

Example 17 to 22 Forming Polymer Electrolyte Multilayer Films onNonionic Carriers

Polymer electrolyte multilayer films containing metal particles wereformed on inorganic alumina carriers. Methods of preparing a catalystand methods of evaluating the activity of the catalyst were conducted inthe same manner as Example 1, except for the kind of a carrier.

The preparation conditions and activity evaluation results of thecatalysts are given in Table 3.

TABLE 3 Layer Cationic polymer Anionic polymer number of Pd H₂O₂ H₂electrolyte electrolyte multilayer content yield selectivity Ex. kindconc. pH kind conc. pH film (wt %) (wt %) (%) 17 PAH 10 mM 9 PSS 10 mM 97 0.18 2.5 62 18 PDDA 10 mM 9 PSS 10 mM 9 7 0.17 2.5 64 19 PEI 1 g/L 5PSS 10 mM 9 7 0.22 1.5 64 20 PAH 10 mM 9 PAA 10 mM 9 7 0.17 1.2 62 21PDDA 10 mM 9 PAA 10 mM 9 7 0.12 1.1 62 22 PEI 1 g/L 5 PAA 10 mM 9 7 0.110.7 57

Example 23 Forming an Anionic Polymer Electrolyte Multilayer FilmComplexed with Metal Precursors on an Anionic Carrier

A polymer electrolyte multilayer film was formed on an anionic resinhaving a sulfonic acid group (SO₃) in the same manner as Example 1,except that an anionic polymer electrolyte (PSS—Pd²⁺) complexed withmetal was used. The anionic polymer electrolyte complexed with metalincludes 10 mM PSS and 0.25 mM K₂PdCl₄ and has a pH of 5.

The anionic polymer electrolyte complexed with metal was repeatedlyapplied on the anionic resin to form a polymer electrolyte multilayerfilm having a layer number of 7, and then the polymer electrolytemultilayer film was reduced in the same manner as Example 1 withoutadditionally introducing metal ions to form an anionic polymerelectrolyte multilayer film complexed with metal particles on theanionic resin, thereby preparing a catalyst. The prepared catalystincludes 0.25 wt % of palladium (Pd).

Thereafter, the activity of the catalyst was evaluated in the samemanner as Example 1. As a result, the yield of hydrogen peroxide is 6.9wt %, and the selectivity of hydrogen is 70%.

Example 24 Forming a Cationic Polymer Electrolyte Multilayer FilmComplexed with Metal Precursors on an Anionic Carrier

A polymer electrolyte multilayer film was formed on an anionic resinhaving a sulfonic acid group (SO₃ ⁻) in the same manner as Example 1,except that a cationic polymer electrolyte (PAH—PdCl₄ ²⁻) complexed withmetal was used. The cationic polymer electrolyte complexed with metalincludes 10 mM PAH and 0.25 mM K₂PdCl₄ and has a pH of 5.

The cationic polymer electrolyte complexed with metal was repeatedlyapplied on the anionic resin to form a polymer electrolyte multilayerfilm having a layer number of 7, and then the polymer electrolytemultilayer film was reduced in the same manner as Example 1 withoutadditionally introducing metal ions to form a cationic polymerelectrolyte multilayer film complexed with metal particles on theanionic resin, thereby preparing a catalyst. The prepared catalystincludes 0.19 wt % of palladium (Pd).

Thereafter, the activity of the catalyst was evaluated in the samemanner as Example 1. As a result, the yield of hydrogen peroxide is 5.8wt %, and the selectivity of hydrogen is 69%.

Example 25 Forming an Anionic Polymer Electrolyte Multilayer FilmComplexed with Metal Precursors on a Cationic Carrier

A polymer electrolyte multilayer film was formed on a halogen-containingcationic (NR₃ ⁺Cl⁻) resin in the same manner as Example 10, except thatan anionic polymer electrolyte (PSS—Pd²⁺) complexed with metal was used.The anionic polymer electrolyte complexed with metal includes 10 mM PSSand 0.25 mM K₂PdCl₄ and has a Ph of 5.

The anionic polymer electrolyte complexed with metal was repeatedlyapplied on the cationic resin to form a polymer electrolyte multilayerfilm having a layer number of 6, and then the polymer electrolytemultilayer film was reduced in the same manner as Example 10 withoutadditionally introducing metal ions to form an anionic polymerelectrolyte multilayer film complexed with metal particles on thecationic resin, thereby preparing a catalyst. The prepared catalystincludes 0.18 wt % of palladium (Pd).

Thereafter, the activity of the catalyst was evaluated in the samemanner as Example 10. As a result, the yield of hydrogen peroxide is 4.3wt %, and the selectivity of hydrogen is 68%.

Example 26 Forming a Cationic Polymer Electrolyte Multilayer FilmComplexed with Metal Precursors on a Cationic Carrier

A polymer electrolyte multilayer film was formed on a halogen-containingcationic (NR₃ ⁺Cl⁻) resin in the same manner as Example 10, except thata cationic polymer electrolyte (PAH—PdCl₄ ²⁻) complexed with metal wasused. The cationic polymer electrolyte complexed with metal includes 10mM PAH and 0.2.5 mM K₂PdCl₄ and has a pH of 5.

The cationic polymer electrolyte complexed with metal was repeatedlyapplied on the cationic resin to form a polymer electrolyte multilayerfilm having a layer number of 6, and then the polymer electrolytemultilayer film was reduced in the same manner as Example 10 withoutadditionally introducing metal ions to form a cationic polymerelectrolyte multilayer film complexed with metal particles on thecationic resin, thereby preparing a catalyst. The prepared catalystincludes 0.14 wt % of palladium (Pd).

Thereafter, the activity of the catalyst was evaluated in the samemanner as Example 10. As a result, the yield of hydrogen peroxide is 2.4wt %, and the selectivity of hydrogen is 65%.

Comparative Example 1

The activity of a commonly-used Pd/C catalyst composed of active carbonsupported with 1 wt % of palladium (Pd) was evaluated in the same manneras Example 1. As a result, after 48 hours of reaction, the yield ofhydrogen peroxide is 0.1 wt %, and the selectivity of hydrogen is 30%.

It can be seen from the result that the activity of the catalystincluding a polymer electrolyte multilayer film of the presentdisclosure is higher than that of a catalyst including no polymerelectrolyte.

Comparative Example 2

The activity of a catalyst including an anionic resin having a sulfonicacid group (SO₃) and doped thereon with 0.23 wt % of palladium (Pd) wasevaluated in the same manner as Example 1. As a result, after 80 hoursof reaction, the yield of hydrogen peroxide is 2.9 wt %, and theselectivity of hydrogen is 68%.

It can be seen from the result that the activity of the catalystincluding the ionic resin formed thereon with a polymer electrolytemultilayer film of the present disclosure is higher than that of acatalyst including no polymer electrolyte layer.

Comparative Example 3

300 mL of an aqueous 10 mM PAH solution was put into a beaker filledwith 10 g of an anionic resin having a sulfonic acid group (SO₃ ⁻) andthen stirred for 20 minutes. Subsequently, palladium ions were dispersedbetween the anionic resin and a cationic polymer electrolyte layer inthe same manner as Example 1, and then the palladium ions were reducedto palladium metal using a reducing agent to prepare a catalyst. Theprepared catalyst includes 0.12 wt % of palladium (Pd).

The activity of the catalyst was evaluated in the same manner asExample 1. As a result, after 80 hours of reaction, the yield ofhydrogen peroxide is 1.4 wt %, and the selectivity of hydrogen is 67%.

It can be seen from the result that the activity of the catalystincluding the ionic resin formed thereon with a polymer electrolytemultilayer film of the present disclosure is higher than that of acatalyst including only a single polymer electrolyte layer.

Comparative Example 4

300 mL of an aqueous 10 mM PAH solution was put into a beaker filledwith 10 g of an inorganic alumina carrier and then stirred for 20minutes. Subsequently, palladium ions were dispersed between theinorganic alumina carrier and a cationic polymer electrolyte layer inthe same mariner as Example 1, and then the palladium ions were reducedto palladium metal using a reducing agent to prepare a catalyst. Theprepared catalyst includes 0.05 wt % of palladium (Pd).

The activity of the catalyst was evaluated in the same manner asExample 1. As a result, after 80 hours of reaction, the yield ofhydrogen peroxide is 0.4 wt %, and the selectivity of hydrogen is 62%.

It can be seen from the result that the activity of the catalystincluding the inorganic alumina carrier formed thereon with a polymerelectrolyte multilayer film of the present disclosure is higher thanthat of a catalyst including only a single polymer electrolyte layer.

Comparative Example 5

300 mL of an aqueous 10 mM PSS solution was put into a beaker filledwith 10 g of a nonionic inorganic alumina carrier and then stirred for20 minutes. Subsequently, palladium ions were dispersed between theinorganic alumina carrier and an anionic polymer electrolyte layer inthe same manner as Example 1, and then the palladium ions were reducedto palladium metal using a reducing agent to prepare a catalyst. Theprepared catalyst includes 0.07 wt % of palladium (Pd).

The activity of the catalyst was evaluated in the same manner asExample 1. As a result, after 80 hours of reaction, the yield ofhydrogen peroxide is 0.8 wt %, and the selectivity of hydrogen is 64%.

It can be seen from the result that the activity of the catalystincluding the nonionic inorganic alumina carrier formed thereon with apolymer electrolyte multilayer film of the present disclosure is higherthan that of a catalyst including only a single polymer electrolytelayer.

Although the various exemplary embodiments of the present disclosurehave been disclosed for illustrative purposes, those skilled in the artwill appreciate that various modifications, additions and substitutionsare possible, without departing from the scope and spirit of thedisclosure as disclosed in the accompanying claims.

1. A method of preparing a catalyst, comprising: alternately applying afirst polymer electrolyte solution and a second polymer electrolytesolution to a carrier to form a polymer electrolyte multilayer film onthe carver, wherein the first polymer electrolyte solution and thesecond polymer electrolyte solution are different from each other, andare cationic or anionic electrolyte solutions, respectively; applying ametal precursor solution to the carrier including the polymerelectrolyte multilayer film formed thereon to disperse metal precursorsin the polymer electrolyte multilayer film; and reducing the metalprecursors dispersed in the polymer electrolyte multilayer film tometals using a reducing agent.
 2. A method of preparing a catalyst,comprising: alternately applying a first polymer electrolyte solutionand a second polymer electrolyte solution to a carrier to form a polymerelectrolyte multilayer film on the carrier, wherein the first polymerelectrolyte solution and the second polymer electrolyte solution arecationic or anionic electrolyte solutions different from each other, andat least one of the first polymer electrolyte solution and the secondpolymer electrolyte solution includes metal precursors complexedtherewith; and reducing the metal precursors dispersed in the polymerelectrolyte multilayer film to metals using a reducing agent.
 3. Themethod of preparing a catalyst according to claim 1, wherein thecationic or anionic polymer electrolyte solution has a pH of 8˜11, andthe metal precursor solution has a pH of 2˜6.
 4. The method of preparinga catalyst according to claim 1, wherein the reducing agent is at leastone selected from among sodium borohydride (NaBH₄), hydrazine (N₂H₄),sodium formate (HCOONa), ammonium hydrogen carbonate (NH₄HCO₃), andhydrogen (H₂).
 5. The method preparing a catalyst according to claim 2,wherein the reducing agent is at least one selected from among sodiumborohydride (NaBH₄), hydrazine (N₂H₄), sodium formate (HCOONa), ammoniumhydrogen carbonate (NH₄HCO₃), and hydrogen (H₂).
 6. A method ofproducing hydrogen peroxide from hydrogen and oxygen using the catalystcomprising: a carrier, a polymer electrolyte multilayer film formed onthe carrier, and metal particles dispersed in the polymer electrolytemultilayer film.